In recent years, the Internet has been widely used, and a user can access various information on websites operated at different locations around the world, and get the information. Accordingly, apparatuses that can perform broadband access such as ADSL (Asymmetric Digital Subscriber Line) and FTTH (Fiber To The Home) have also rapidly begun to be widely used.
IEEE Std 802.3ah (registered trademark)—2004 (Non-Patent Literature 1) discloses one scheme for a passive optical network (PON) which is media sharing communication where a plurality of optical network units (ONUs) perform data transmission with an optical line terminal (OLT) by sharing an optical communication line. Specifically, there are specified an EPON (Ethernet (registered trademark) PON) where all information including user information that passes through a PON and control information for managing and operating the PON is communicated in Ethernet (registered trademark) frame format, and an EPON access control protocol (MPCP (Multi-Point Control Protocol)) and an OAM (Operations Administration and Maintenance) protocol. By exchanging MPCP frames between the optical line terminal and an optical network unit, the subscription and unsubscription of the optical network unit, upstream access multiplex control, and the like, are performed. In addition, Non-Patent Literature 1 describes a registration method for a new optical network unit, a REPORT indicating a bandwidth allocation request, and a GATE indicating a transmission instruction which are performed by MPCP messages.